Dried packaged convenience foods or mixes, such as, for example, soups, casseroles, salads, pasta, rice, cereal, snacks, and the like, are popular. Such foods or mixes frequently contain various types of dehydrated fruits and vegetables (generally with water activities of less than about 0.5 and often less than about 0.4) along with other food components. Such dehydrated vegetables are often prepared using gentle drying conditions (e.g., freeze drying, vacuum drying, and the like) in order to preserve as much as possible the desirable attributes of the fresh fruits and vegetables. Unfortunately, such dehydrated fruits and vegetables (especially high quality, reduced density freeze dried products) tend to be fragile and easily broken due to inevitable stresses (e.g., free fall impact, compression, abrasion, and the like) encountered during handling, packing, and storage, and generally do not resemble their fresh counterparts in terms of color, appearance, and/or texture.
Numerous attempts have been made to prepare dehydrated fruits and vegetables having improved properties. Japanese Patent Publication 1983/000106764 (Jun. 16, 1983) provided a process of drying foods including fruits (e.g., banana, strawberry, and the like) by drying in microwave oven having an electrical field intensity of about 0.01 to about 0.2 W/cm2, irradiated with microwave radiation, and then heated externally with an auxiliary heat source (e.g., hot-air heating, infrared heating, electrical heating) while maintaining the temperature below a specific level (about 98 ° C.) to obtain the dried foods.
Japanese Patent 6,217,683A2 (Aug. 9, 1994) used a process whereby vegetables were cooled to a temperature equal or below freezing temperature, subsequently heated, and dried in hot oil and under vacuum to obtain an improved dry vegetable product.
U.S. Pat. No. 5,955,130 (Sep. 21, 1999) used flash blanching of vegetables in about 100% saturated steam, steam cooking in 35 to 65% saturated steam, and cooking and drying the vegetables by exposure to infrared radiation to obtain a vegetable product particularly useful as a binder, filling, or topping in complex foods.
U.S. Pat. No. 6,004,590 (Dec. 21, 1999) described a process for producing dehydrated vegetables including preparing the vegetables, holding the prepared vegetables for a time and at a temperature from 45 to 70° C. to activate pectinmethylesterase, blanching, and drying. The drying includes exposure to microwave radiation at a pressure below atmospheric pressure.
U.S. Pat. No. 6,268,012 (Jul. 31, 2001) provides a method for producing dried vegetables wherein substantially all of the cells are reportably undamaged and damage to cellular structure is minimized. A gentle, four stage drying process using a temperature of about 60° C. and controlled humidity is used to avoid excessive temperature and humidity differences between the product and the drying medium.
European Patent 1,009,246B1 (Nov. 20, 2002) described a process of treating with pectinmethylesterase and added pectin to improve the firmness of fruits or vegetables which do not possess such enzyme naturally.
Although these methods can provide improved dehydrated vegetables after rehydration (Aw of 0.5 or less), the dehydrated vegetables, regardless of improved drying methods or other treatments, still tend to be brittle and give a powdery, unnatural appearance. In addition, such dehydrated vegetables are susceptible to breakage during handling, packing and shipping.
An alternate method, namely infusion, was developed to produce non-brittle, intermediate moisture vegetables with Aw greater than 0.5 and typically ranging from 0.5 to 0.9. U.S. Pat. No. 3,623,893 (Nov. 30, 1971) used super-atmospheric pressures (i.e., 200 to 4000 psi) to infuse foods, including vegetables, with an aqueous infusion cocktail containing propylene glycol, potassium sorbate, glycerol, and salt. Of course, the use of such high pressures would involve high capital expense if such a system were used commercially.
U.S. Pat. No. 3,745,027 (Jul. 10, 1973) provided a method for cooking vegetables in an infusion, mixture containing, for example, glycerol, salt, propylene glycol, potassium sorbate, and water. For example, diced carrots cooked for 15 minutes in the infusion mixture and then soaked for 6 hours in the infusion mixture were reported to have “acceptable eating qualities and microorganic stability.”
U.S. Pat. No. 4,832,969 (May 23,1989) provides improved dried green vegetables using an infusion cocktail containing a polyhydric alcohol, a sugar, an alkaline buffering system or agent (i.e., sufficient to obtain a cocktail pH of about 6 to 8), an inorganic bittering agent (e.g., KCl and/or MgCl2), a surfactant, salt, and an anti-oxidant (e.g., vitamin E, tocopherol, BHA, BHT, or mixtures thereof). After treatment with the infusion cocktail, the vegetable pieces are dried to a water activity of about 0.3 to 0.85 at a temperature of less than about 135° F. The resulting dried green vegetables are reported to have superior color retention for extended time periods even at room temperature storage, superior texture upon rehydration, and excellent rehydration rates.
U.S. Pat. No. 4,889,730 (Dec. 26, 1989) provides a fruit or vegetable snack product prepared by using a sugar soaking step to prevent collapse and shrinkage of the fruit or vegetable pieces during drying, mixing the fruit or vegetables pieces with a foam composition, and drying the resulting agglomerated product.
U.S. Pat. No. 4,946,693 (Aug. 7,1990) provides a process for preparing intermediate moisture vegetables. In this process, vegetables are blanched or cooked, preferably using a microwave oven, and then partially dried (i.e., water content of 45 to 55 percent). The dried vegetables are then dry mixed with salt (and optionally sodium glutamate if the vegetables are not cooked using a microwave oven); an anti-mycotic agent can also be added.
U.S. Pat. No. 4,948,609 (Aug. 14, 1990) provides puffed dried vegetables using an infusion solution containing at least one reducing agent, a proton donor, and a disaccharide in order to prevent discoloration, followed by vacuum drying.
U.S. Pat. No. 5,110,609 (May 5,1992) provides a method for producing intermediate moisture vegetables wherein the vegetables are partially dehydrated to a moisture content of 26 to 60 percent and then stored in an oxygen free atmosphere.
U.S. Pat. No. 5,368,873 (Nov. 29, 1994) provides a method for producing dehydrated vegetables involving immersing the vegetable in a liquid bath containing an osmotic agent capable of infusing into the vegetable tissue and forming an amorphous solid upon drying, removing excess osmotic agent, and then drying. Suitable osmotic agents include monosaccharides, disaccharides, polyalchohols which form solids at room temperature, corn syrups, and mixtures thereof.
U.S. Pat. No. 5,925,395 (Jul. 20, 1999) provides a method for preserving fresh vegetables whereby the vegetables are treated with a preservative solution containing water, calcium ions, and optionally ascorbic acid or erythorbic acid. The resulting vegetables are then stored at a non-freezing temperature less than 20° C. If stored at ambient temperatures, microbial contamination is possible.
Japanese Patent Publication 11-318375 (Nov. 24, 1999) provides a method for producing dried vegetable or fruit products by adding an edible oil or fat and a diglycerol fatty acid monoester to the vegetable or fruit and then drying the mixture.
U.S. Pat. No. 6,159,527 (Dec. 12, 2000) provides a method and apparatus for infusing fruit, including vegetables, using an infusion cocktail containing sugar wherein the flowrate and infusion cocktail are controlled such that the fruit or vegetables are exposed to progressively higher concentrations of sugar of a level only sightly higher than the sugar content of the fruit or vegetables being infused.
International Patent Publication WO 0,201,968A1 provides a method for preparing a substantially dehydrated vegetable product, in particular a herb or aromatic spice, having an Aw of about 0.5 to 0.7 by infusing the vegetables with a substantial quantity of mineral salt, carbohydrate, and/or polyol and drying the infused vegetables.
U.S. Pat. No. 6,403,134 (Jun. 11, 2002) provides a method for preparing intermediate moisture vegetables by (a) infusing vegetables with an antimicrobial infusion cocktail at a temperature of greater than about 50° F. for about 15 to about 180 minutes, wherein the antimicrobial infusion cocktail comprises an aqueous solution of (1) a water-soluble, predominantly lower molecular weight, low sweetness carbohydrate, (2) a polyhydric alcohol, (3) salt, (4) a non-inorganic sweetness depressant agent, and (5) nisin-containing whey derived from a nisin-producing culture; (b) collecting the vegetables and removing excess antimicrobial infusion cocktail; (c) drying the collected vegetables to a water activity of about 0.5 to about 0.9 to form the intermediate moisture vegetables; and (d) packaging the intermediate moisture vegetables.
Although these infusion methods can provide intermediate moisture fruits and vegetables with improved mechanical properties (i.e., non-brittle), while maintaining water activities greater than about 0.5, such vegetables typically have less than desirable organoleptic properties. For example, such fruits and vegetables often have a poor, heavy, and/or candy-like appearance and/or undesirable taste profile (e.g., too sweet or salty) due to high levels of humectants. Over-drying of such fruits and vegetables (e.g., water activities less than about 0.5) generally results in hard glassy products with poor hydration characteristics.
Thus, there remains a need for improvements in methods of providing intermediate moisture or infused fruits and vegetables, auspiciously for more delicate fruits and vegetables such as strawberries, broccoli, mushrooms, and the like. The present method, which is both simple and inexpensive, provides such improvements. Indeed, the present method allows the preparation of dried fruits and vegetables which are shelf stable and non-brittle as indicated by a drastic reduction of fines and/or broken pieces after drying and/or storage, shipping, and handling as compared to conventionally dried fruits and vegetables. The present dried fruits and vegetables have improved quality with a more natural color and more intact, natural appearance than conventionally dried fruits and vegetables and improved handling and shipping properties due to increased resistance to fracture or breakage of the individual pieces.